It is known in the art to fabricate microelectronic devices, such as semiconductive devices and integrated circuits, by the use of a masking-etching operation to open windows in layers of various electronic circuit materials, such as semiconductors, conductors, and insulators. In such prior art methods, the masking material employed may be an organic polymer. The etching step then consists of immersion of the masked device in an etching solution, such as an aqueous solution of an acid. See, e.g., the processes described in U.S. Pat. Nos. 3,885,076 and 4,080,721.
There are a number of disadvantages associated with such prior art processes which drastically and adversely affect the yield from such processes. The masking material used in such processes is generally an organic polymer, which is usually solvent coated onto the device to be masked, or deposited thereon by vapor phase deposition in a vacuum chamber. After the masking material has been deposited and selectively hardened or crosslinked photochemically or by an electron beam, the masked device must be withdrawn from the vacuum chamber for etching with etching solution. When the masked device is withdrawn from the vacuum chamber and etched, dust particles and other materials may adhere to the surface of the device, resulting in a defective device. Physical damage to the devices may occur during such handling. When the masked device is etched, the etching solution may leave impurity particles on the surface of the device to again result in a defective device. Other causes for defective devices in such an etching operation are also known to those skilled in the art.
Various prior art methods for making microelectronic devices are shown, for example, in U.S. Pat. Nos. 3,885,076; 3,920,454; 4,080,721; 4,102,733 and 4,114,255. U.S. Pat. No. 3,885,076 is illustrative of the prior art process in inserting, withdrawing and then re-inserting the work piece into a vacuum chamber. In FIG. 1 of that patent, a work piece is coated with a film of a polymer which is then selectively crosslinked by exposure to an electron beam in accordance with a desired pattern. In FIG. 2 of that patent, the work piece was withdrawn from the vacuum chamber and the uncrosslinked portion of the film was dissolved to develop the pattern. FIG. 3 of that patent illustrates the etching of the portion of the substrate unprotected by the crosslinked film. After further processing, the work piece may then be re-inserted into the vacuum chamber for additional treatment, such as doping of the semiconductor by means of ion implantation.
In view of the foregoing, there is a continuing need for an improved method for making microelectronic devices.
Accordingly, it is an object of present invention to provide an improved method for the fabrication of microelectronic devices.
It is another object of the present invention to provide a novel method for the making of microelectronics devices which can be carried out entirely in the dry state, without the need for any etching solutions.
Other objects of the invention can be gathered from the following disclosure.